“White” LEDs have been used in numerous devices/applications such as flashlights, task lights for motor vehicles and the like. White LEDs generally include a blue LED with a phosphor coating that emits yellow light which mixes with the blue light to provide light that is perceived to be primarily white, with a slight bluish tint. Another type of white LED utilizes a combination of blue, red, and green LEDs to produce white light. Due to the efficiency of white LEDs, the use of white LEDs in applications such as vehicles and the like having a limited supply of electrical power has been increasing.
Although the light produced by a white LED has a color that is acceptable for task lights and the like, the light is typically not focused enough to provide efficient lighting for such applications. Various lenses, reflectors, collimators and the like have been developed to focus or direct the light from LEDs. Referring to FIG. 1, a prior art collimator 10 includes a body 11 made of a polymer material. The body includes a flat end surface 12 and tapered side surfaces 13 that gives the collimator 10 a generally conical shape. A cavity 14 has a generally cylindrical side surface 15, and an open end 16 that receives white LED 17. A convex surface 18 faces the white LED 17. The light from white LED 17 incident upon cylindrical sidewall 15 refracts from the tapered side surfaces 13, and exits the collimator 10 through flat end surface 12. The convex surface 18 reflects light internally from white LED 17 and directs the light through flat end surface 12.
The collimator 10 of FIG. 1 produces a light intensity distribution curve 19 illustrated in FIG. 2. Thus, although collimator 10 does direct the light in a beam, the light intensity distribution is quite uneven. Also, although white LEDs generally produce a light having a color suitable for use as a task light and the like, white LEDs tend to produce light having a yellowish tint at the peripheral edges of the light pattern.
Accordingly, a way to direct and focus light from a white LED in an efficient manner would be advantageous.